High-cycle rotating bending fatigue test of notched specimens to enhance N-SIF based fatigue assessment approaches

This paper presents the results of a relatively wide experimental campaign to complement test data already available in open literature. Fatigue tension tests of square-section notched specimens were carried out a few years ago to support the validation of fatigue assessment approaches based on Notch Stress Intensity Factor (N-SIF), e.g. the Strain Energy Density approach and the Peak Stress Method, although limiting the run-out up to 2·106 cycles. Having in mind the target of ships and offshore structures, experiencing during their lives about 108 cycles, a few series of rotating bending fatigue tests of variously notched specimens made by different structural steels were carried out up to 5·107 cycles as run-out target. About 100 specimens were prepared and tested, resulting into a rather comprehensive data set including also measurements of local notch geometries. It turned out that the effects of the notch geometry in general and that of the notch radius at tip in particular were quite significant on the fatigue strength. Useful comparisons with numerical finite element simulations applying the Strain Energy Density approach are also outlined in the analysis of the obtained experimental data.